The present invention relates to a grinding machine for a bar member for magnetic heads and a method of grinding the bar member.
Magnetic head elements, which are used in magnetic disk drive units, etc., are manufactured by forming magnetizable layers and non-magnetizable layers on a ceramic substrate (a ceramic wafer). A lot of magnetic head elements are formed on the ceramic substrate. Each of the magnetic head elements includes: a magnetic head element section, which has a magnetoresistance effect head (a regenerating head) including an MR element, etc. and an electromagnetic induction head (a recording head); an monitor ELG element section, which is arranged adjacent to the magnetic head element section; and terminals (pads) connected to the magnetic head element section and the ELG element section.
The magnetic head elements are manufactured by the steps of: forming the magnetic head element sections, the ELG element sections, the terminals, etc. on the wafer; cutting the wafer so as to form a plurality of thin bar member; and grinding a side face of each bar member. Tens of the magnetic head element sections are linearly arranged in each bar member.
The side face of the bar member is ground so as to adjust a height of a sensing part including the MR element, which is called a strip height or an MR height, to a prescribed height. The lower sensing part has higher sensitivity. These days, in the magnetic head elements, required accuracy of the strip height is 0.8 xcexcmxc2x10.2 xcexcm. But, in the near future, it must be higher: 0.3 xcexcmxc2x10.03 xcexcm.
Since the strip height must be highly precisely adjusted, the ELG element section, whose structure is equal to that of the magnetic head element section, is provided for each magnetic head section. The ELG element section is simultaneously ground, and its resistance value is measured so as to monitor the sprit height of the corresponded magnetic head element section. With this action, the magnetic head elements can be ground with high accuracy.
A jig for grinding the bar member is shown in FIG. 21. The jig is disclosed in the U.S. Pat. No. 5,607,430.
The jig 10 is made of a metal or a ceramic. The bar member 12 is adhered onto the jig 10 with an adhesive, e.g., wax. A face of the bar member 10 to be ground is pressed onto a grinding plate, e.g., a lapping plate (not shown), with the jig 10 so as to grind the face to be ground.
The jig 10 includes a plurality of slits 14 having proper patterns and a plurality of actuator holes 16. Actuators, e.g., air cylinder units (not shown), are respectively provided in the actuator holes 16.
When the bar member 12 is ground, the actuators are driven to apply force to the jig 10. Since the jig 10 has the slits 14, the jig 10 can be bent by changing output force of the actuators. By bending the jig 10, pressure applying to each part of the bar member 10, from a bottom face, can be precisely controlled. Namely, the pressure applying to each magnetic head element section can be precisely controlled, so that grinding rate for each magnetic head element section can be controlled.
However, the conventional grinding machine and the conventional grinding method have following disadvantages.
As described above, the jig 10 is made of a metal or a ceramic having high strength, so the output force of the actuators must be great so as to bend the jig 10. In spite of forming the slits 14, it is difficult to bend the tough jig 10. Namely, it is difficult to precisely partially control the pressure applying to the parts of the bar member 12. Especially, it is very difficult to grind the bar member 12 with higher grinding accuracy. Further, a cost for manufacturing the jig 10 having the slits 14 must be increased.
An object of the present invention is to provide a grinding machine and a method of grinding, which are capable of grinding a bar member for a magnetic head with higher grinding accuracy.
To achieve the object, the grinding machine of the present invention comprises: means for holding a bar member, the holding means heading a first face of the bar member, which is to be ground, downward; a grinding plate for grinding the first face of the bar member; an actuator for pressing a second face, which is an opposite face with respect to the first face, of the bar member held by the holding means so as to press the first face onto the grinding plate; and means for monitoring a resistance value of a sensing part of an ELG element section of the bar member so as to adjust a strip height of a magnetic head section of the bar member.
The grinding method of the present invention comprises the steps of:
holding a bar member and heading a first face of the bar member, which is to be ground, downward; pressing a second face, which is an opposite face with respect to the first face, of the bar member, by an actuator, so as to press the first face onto a grinding plate and grind the same; and
monitoring a resistance value of a sensing part of an ELG element section of the bar member so as to adjust a strip height of a magnetic head section of the bar member.
Another method of the present invention comprises the steps of: adhering flexible film onto a second face of a bar member, which is an opposite face with respect a first face thereof to be ground; holding the bar member with the flexible film and heading the first face of the bar member downward; pressing the second face of the bar member and the flexible film, by an actuator, so as to press the first face onto a grinding plate and grind the same; and monitoring a resistance value of a sensing part of an ELG element section of the bar member so as to adjust a strip height of a magnetic head section of the bar member.
In the present invention, the second face of the bar member is pressed, directly or with the flexible film, by the actuator, so that pressure can be differently and precisely applied to each element and the grinding accuracy can be improved.